Metaeldehyde is a highly selective snailicide,commonly used to control molluscs such as snails,snails,slugs and other crops on rice,tobacco,fruits,vegetables and other crops.In recent years,snails and other mollusks have become widespread in some orchards and vegetable gardens.They have become new pests in orchards and vegetable gardens.They are more common in sunny mornings and evenings after rain.At the same time secrete special mucus,seriously affecting fruit production and safety quality.Snails belong to mollusks,not insects.Traditional insecticides have a poor control effect on snails.6%metaeldehyde granules are often used as medicaments for mollusc control.Spread on the soil surface or around the crops.Applying medicine at the peak of the event.Due to the special odor of 6%metaeldehyde granules,it can attract snails to eat.Taking advantage of this feature,when snails feed or contact crops,metaeldehyde enters the snail body,making the acetylcholine ester in the snail body.The enzyme is quickly released,destroying the body fluids of the snail,and causing massive dehydration to death.There are relatively few domestic and foreign reports on the analysis method of metaeldehyde residues.The research on the dynamics of residue digestion on fruits has not been reported in China.In order to understand the residual situation of 6%metaeldehyde granules on dragon fruit and kiwifruit,this paper conducts research based on the field experiment of 6%metaeldehyde granules on dragon fruit and kiwifruit.To make reference and safety evaluation for the rational use of 6%metaeldehyde granules in dragon fruit and kiwifruit,and put forward the guidelines for the rational use of metaeldehyde in dragon fruit and kiwifruit.In this paper,the method of residue analysis of metaeldehyde in dragon fruit,kiwifruit and soil was established.In the concentration range of 0.01~1 mg/L,the linear correlation coefficient is 0.9995,and the method has good linearity.The optimized conditions were used to test the recovery rate of the blank sample matrix at different concentrations.The results showed that when the concentration of metaldehyde in the dragon fruit was 0.01 mg/kg~1mg/kg,the average recovery was 71%~88%;when the concentration of metaldehyde in the fruit of dragon fruit was 0.01 mg/kg~1 mg/kg,the average recovery rate is 68%~85%;when the concentration of metaldehyde in the whole kiwifruit fruit is 0.01 mg/kg~1 mg/kg,the average recovery rate is 71%~90%;when the concentration of metaldehyde in the soil is 0.01 mg/kg~1 mg/kg,the average recovery rate is 73%~83%.The results show that the method is accurate and reliable,and meets the requirements of pesticide residue analysis and detection for different concentrations of recovery rate and relative standard deviation.Digestion dynamic experiment:The field digestion dynamics of metaldehyde in dragon fruit and kiwifruit were studied through field trials in six places in 2018.The results showed that the degradation of metaldehyde on soil conformed to the first-order reaction kinetic model.The half-life of metaldehyde on dragon fruit soil is 3.73 days in Guangdong province and 2.83 days in Guangxi province.The half-life of metaldehyde on kiwi fruit soil is 3.52days in Guangdong province and 3.19 days in Hunan province.The test shows that metaldehyde is a pesticide that is easily degradable in the environment.Final residue experiment:6%metaldehyde granules were applied at a recommended low dose of 0.9 g a.i/m~2 and a high dose of 1.35 g a.i/m~2.Samples of acetaldehyde in dragon fruit were sampled at 14,21,and 28 days after the last application of metaldehyde to determine the residual amount of metaldehyde in dragon fruit in six areas.Sampling to determine the residual amount of metaldehyde in kiwifruit in six areas,the residual amount was less than the limit of quantitation 0.01 mg/kg.It shows that the scientific use of metaldehyde under the recommended conditions will not cause harm to the growth of dragon fruit and kiwifruit,nor will it affect human health.The cause of undetected may be because the metaldehyde particles are easily washed away by rain and easily degraded,and the specific situation needs to be further studied.Based on the final residual data of metaldehyde in kiwifruit and dragon fruit,the long-term dietary intake risk was evaluated.The results showed that the long-term dietary intake risk quotient of metaldehyde in kiwifruit and dragon fruit was 11.1%under the conditions of0.9~1.5 g a.i/m~2 application concentration 2~3 times,under various picking intervals The risk of dietary intake is low and usually does not pose an unacceptable risk to the health of the general population. |